function scaledData = coarsegrain(data,tau)
% scaledData = coarsegrain(data,tau)
%
% OVERVIEW: generate the consecutive coarse-grained time series
%
% INPUTS:
% data : Vector containing the original seires
% tau : scale factor (if tau = 1 returs the original series)
% OUTPUTS:
% scaledData : the coarse-grained time series at the scale factor tau
%
% Written by: Giulia Da Poian <giulia.dap@gmail.com>
% REPO:
% https://github.com/cliffordlab/PhysioNet-Cardiovascular-Signal-Toolbox
% COPYRIGHT (C) 2016
% LICENSE:
% This software is offered freely and without warranty under
% the GNU (v3 or later) public license. See license file for
% more information
if nargin < 2
error('Wrong number of input arguments');
end
L = length(data);
J = fix(L/tau);
scaledData = zeros(1,J);
if tau < 1
error('The scale factor must be a positive integer number');
elseif tau == 1
scaledData = data; % return orignal series
return
else
for idx=1:J
scaledData(idx) = mean(data((idx-1)*tau+1:idx*tau));
end
end